Leica tps1100, Руководство пользователя, Страница: 257 / 1154

GeoBASIC Reference Manual 2.GeoBasic Constructs
2-28 TPS1100-Version 1.30
♦
If
a
is greater than
b
,
Stat1
will be executed. If
a
is smaller than
b
,
Stat2
will be executed. The ELSE case means that neither a is greater b , nor a is
smaller
b
— hence
a
equals
b
. In that case
Stat3
is executed.
IF a > b THEN
Stat1
ELSEIF a < b THEN
Stat2
ELSE 'a = b
Stat3
END IF
Note In general the branch conditions in the
IF
-Statement must neither be
exclusive nor complete. Hence the compiler will not check if any branch
is accessible.
♦
The built in function Abs computes the absolute value of a number, i.e. takes a
number and computes its value as a non-negative integer ("forgets its sign"). It
can be written as the following program that does nothing if
x
is already non-
negative, and converts x to a positive number if the current value is negative.
The empty
ELSE
case can be omitted.
IF x < 0 THEN
x = -x
END IF
♦
Another example is given in the next Section 2.6.2.2 on The SELECT-
Statement.
2.6.2.2 The SELECT-Statement
The expression is evaluated and compared to the constants. If a constant equal to
the value of the expression is found, the corresponding statement sequence is
executed. If no constant equals the expression and there is a
CASE ELSE , the
statement sequence following this is executed, otherwise nothing more is done.
Execution then continues with the statement after
END SELECT
.
The expression and the constants must be of a simple type or strings, and the
constants should all have different values. The order of the constants in the list,
and the order of the lists in the
SELECT
-statement is irrelevant as far as the effect
of the statement is concerned; however, the constants will be checked for equality
in the order in which they appear, so if the most frequent case is put first, this will
likely result in faster execution.